Nutritional Megaloblastic Anemia

Nutritional megaloblastic anemia, also called nutritional macrocytic anemia, is common in infants/toddlers especially under 2 years; previously common in northern/northwestern rural China but markedly declining recently. It is mainly caused by vitamin B12 or folate deficiency. Features: all-stage RBCs are larger than normal, hemoglobin falls more obviously than red-cell count, granulocytes and platelets decrease, granulocyte nuclei shift right, marrow shows megaloblasts; treatment with vitamin B12 and folate is effective.

Common Symptoms

Lymphadenopathy; tremor; fatigue; diarrhea; malnutrition; convulsions; hyperreflexia; hyporeactivity

Causes and Pathogenesis

Vitamin B12 is mainly in animal foods (liver/kidney/meat rich, milk low); folate is rich in fresh green leafy vegetables, liver and kidney. B12 requirement: adults ~2-3 ug/day, infants ~0.5-1 ug/day; folate: adults ~50-75 ug/day, infants ~10-20 ug/day. Delayed complementary feeding or long-term food faddism in older children causes B12/folate deficiency. Chronic diarrhea, small-bowel resection, regional ileitis and intestinal TB impair B12/folate absorption; liver disease, acute infection, achlorhydria, vitamin C deficiency impair metabolism/utilization. Premature/newborn/infant rapid growth increases needs; recurrent infection raises B12/folate consumption. Fetal B12/folate stored in liver via placenta; deficient mothers lead to low newborn stores. Mechanism: both folate and B12 are essential for nuclear DNA synthesis; cell proliferation hinges on DNA replication. Folate in liver is converted by dihydrofolate reductase to active THFA, the one-carbon-transfer coenzyme. B12 participates in four key reactions: (1) converts inactive methyl-THFA to active THFA, raising folate utilization; (2) promotes folate entry into cells; (3) participates in deoxythymidine synthesis - B12 deficiency causes DNA synthesis failure via folate-metabolism block, explaining why B12 improves folate-deficiency anemia and large folate doses mask B12 hematologic changes; (4) B12 enables fat-metabolism products to enter the TCA cycle, related to myelin lipoprotein formation, maintaining central/peripheral myelinated fibers - B12 deficiency causes neuropsychiatric symptoms; folate does not participate and cannot reverse B12 neurologic damage, but increases hematopoietic-cell B12 use and may worsen neuro symptoms.

Treatment

Drug therapy, supportive therapy

Preventive Measures

Prevention starts with improving population diet and lifestyle; high-risk individuals should have awareness of drug prophylaxis. WHO recommended daily folate: infants <6 months 40-50 ug, 7-12 months 120 ug, 1-12 years 200 ug, >13 years 400 ug, pregnant women 800 ug.

Department to Visit

It is recommended to visit the Hematology department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.